Systems for monitoring pupil size and pupil responsiveness characteristics are well known in the art and are generally referred to as pupilometry systems or, simply, pupilometers. One early pupilometer is described in U.S. Pat. No. 3,533,683, which issued to Stark et al. on Oct. 13, 1970 and is entitled “Dynamic Pupilometers Using Television Camera System” (incorporated herein by reference). The Stark et al. system employed a television camera system, a digital computer system, an infrared light source, and a visual light stimulator for determining the instantaneous size of a pupil as an eye (or neurologic pupilary control system) of a patient was exposed to various stimuli. Like the early Stark et al. system, conventional pupilometers measure, for example, the diameter of a pupil before and after the pupil is exposed to a light stimulus pulse and also measure the rates at which the pupil may constrict and dilate in response to the initiation and termination of the light stimulus pulse. Pupilometers may comprise hand-held units or, alternatively, may comprise desk or table-mounted, stand-alone units. Pupilometers also generally include some mechanism for ensuring that an imager within the pupilometer is properly positioned in relation to a pupil to be imaged. For example, U.S. Pat. No. 5,646,709 (incorporated herein by reference), issued to Elbert P. Carter, describes an electronic centering system for ensuring that a pupilometer is properly positioned in relation to a pupil to be imaged. Similarly, U.S. Pat. No. 5,187,506 (incorporated herein by reference), issued to Elbert P. Carter, describes an eye orbit housing for ensuring proper positioning between a pupilometer and an eye of a subject prior to the initiation of a pupilary scanning procedure.
Those skilled in the art will appreciate, however, that for a pupilometer to have maximum utility maximum flexibility should be provided for positioning the imager. For example, in the case of a hand-held system few, if any, restrictions should be placed upon the orientation of the imager prior to enabling an imaging function. The reason for this is that medical personnel at, for example, an accident site may have difficulty in positioning an imager in a prescribed position for acquiring pupilary response data. Thus, it is believed that, for hand-held units in particular, a need exists within the pupilometer field for improved data acquisition and processing systems and methods, as such systems and methods may substantially reduce system dependence on imager orientation and may allow pupilometers to become more user friendly.
Similarly, those skilled in the art will appreciate that a need exists for pupilometers that are capable of evaluating more than a mere pupilary response to light stimulus pulses. For example, it is believed that a substantial need exists for a pupilometer that is capable not only of measuring changes in pupilary diameter in response to one or more light stimulus pulses, but also of evaluating pupil shape and/or segmental responses to a visual stimulus. Stated somewhat differently, it is believed that a substantial need exists for a pupilometer having a pupilary shape irregularity or non-uniformity detection capability.
Finally, it is believed that a substantial need exists for pupilometer-based diagnostics systems, as such systems may provide medical practitioners with a cost effective, noninvasive means for gathering and assessing numerous physiologic parameters.
For example, the present invention can be used to screen for Glaucoma, which is the second leading cause of blindness in the world. Visual field perimetry is presently used for diagnosing Glaucoma. In visual field perimetry, a white background and multiple green flicker sources are used. The green sources are randomly turned on for approximately one second durations and the subject patient is asked to press a button if he/she sees a green light. The procedure is repeated until the entire visual field is mapped for each eye. Loss of visual field sensitivity is indicative of Glaucoma.
The current standard of care for Glaucoma detection, however, suffers form inaccuracy and human/patient error. The current standard of care relies on the patient to respond to his or her visual detection of green light by pressing a button. The patient has a limited window of time in which to respond to the green light. Thus, if the patient is not concentrating or responds too quickly or too slowly, the perimetry device will not register the patient's response, and the accuracy of the diagnosis is compromised. Furthermore, current perimetry devices are large machines that are immobile. They are for use in doctors' offices only. Thus, a need exists for improved systems and methods for Glaucoma detection, and the present invention meets these needs and solves the problems associated with standard techniques.
Another area of diagnostic need relates to assessing the level of brain function to diagnose disorders such as autism, age-related disorders, and drug impairment or intoxication. Neurological exams today do not typically include pupilometry beyond the use of a pin-light. Currently, expensive and/or time-consuming tests are required to diagnose impairment of brain function. And, the pin-light test is subjective, non-quantifiable, and inaccurate. The present invention solves these by providing a method and system to closely track the pupil while presenting the eye with a moving visual stimuli to determine the level of coordination. The present invention is capable of quantifying tracking errors, which might occur in the course of a neurological exam, and reduces the subjectivity and increases the repeatability of exams to assess brain function.
Another area of diagnostic need is diagnosis of neurological disease or trauma. Dermatome mapping of patients is commonly done with a pin-prick to determine the level of dorsal root or spinal cord injury. This test, however, is subjective and usually requires cognitive response from a patient. There exists a need for noninvasive diagnosis of neural damage or trauma. The present invention fills that need by providing a means of quantitatively measuring pupilary response to noxious stimulation. Furthermore, this invention is useful in diagnosing dorsal root and spinal cord injuries in unconscious patients with no cognitive response capabilities. It is further useful in diagnosing and monitoring the progression of demyelinating diseases such as multiple sclerosis, which affects conduction velocity through nerve fibers. In addition, testing the level of epidural anesthetic block may be accomplished using pupilometry with this automated stimulus control.
Finally, an area of diagnostic need relates to testing the functional integrity of auditory pathways, i.e., hearing screening. Particularly with infants, hearing has been subjectively screened using stimuli such as in a clap test while observing the startle response. Other tests, such as EEG-type brain stem audible evoked potential (AEP) monitoring systems have been used, but require attachment of electrodes to the scalp and are cumbersome to use. Middle ear tone-feedback monitoring is also used, but is not capable of measuring latency information. The present invention solves these and other problems associated with the prior art by providing hearing screening using objective pupilometer-based testing systems and methods. The pupilometer-based systems are not cumbersome, are easy to use and provide latency information for diagnosing and monitoring the progression of demyelinating diseases.